The present invention relates to a controller for driving a brush-less motor, and also to a conveyor system having the controllers.
FIG. 5 is a block diagram illustrating the prior art controller for driving the brush-less motor. This controller comprises a control unit 51, an electric-current controller 52 and a magnetic-pole detector 53. In general, the brush-less motor 54 comprises a plurality of stators each consisting of an electromagnet, a rotor with magnetic poles, and a plurality of magnetic-pole sensors for sensing the angular position of the rotor""s magnetic poles. Hall-ICs are widely used as such sensors. Each of them is provided in the form of a single package in which a Hall-effect semiconductor, an amplifier for amplifying a weak signal output from the semiconductor, a Schmidt-trigger circuit converting the amplified signal into a square wave, a power regulator circuit and a temperature compensation circuit.
The control unit 51 receives control signals from a superordinate device such as a sequencer or a central computer. These control signals will be processed in a prescribed manner, before supplied to the current controller 52. The control signals output from the superordinate device include those which turn on or off the brush-less motor 54, change rotational speed thereof and/or switch over the direction of its rotation from forward to reverse, or vice versa.
The magnetic-pole detector 53 successively receives from the Hall-effect semiconductor a series of signals (i.e., polar signals) representing the angular position (viz., rotational phase) of the poles-carried by the rotors. Those signals will thus be converted into pulse waves, before supplied to the current controller 52.
The current controller 52 treats with both the processed signals delivered thereto from the control unit 51 and pole detector 53, according to a given program. Consequently, an electric current that is being applied to each of those stators built in the brush-less motor 54 will thus be turned on or off and/or adjusted in intensity so that the motor rotates at command of the controller 52.
The brush-less motor as summarized above may be used for example as a prime mover in a roller conveyor. The present applicant has been developing a conveyor system comprising a drive roller provided with a built-in brush-less motor, as disclosed in the Japanese Patent Laying-Open Gazette No. 10-279047.
In general, a plurality of brush-less motors have to be incorporated in each of the conveyor systems of this type, and each motor necessitates a controller of the described structure. In order to exactly transport articles along the conveyor, a superordinate control device will output command signals to the respective controllers.
Where there is any need to control the conveyor system in a more sophisticated manner or more accurately, it may be feasible to enrich and enhance the functions of each motor controller. In detail, a microcomputer and/or complicated logic circuits may be built in the controller, for that purpose.
If however those many controllers in each conveyor system had to be so highly functional apparatuses, then an overall manufacture cost of the whole system would rise to an intolerable extent.
Objects of the present invention are therefore to provide a brush-less motor with a functional, accurate and inexpensive controller, as well as a conveyor system comprising such a brush-less motor.
In accordance with the present invention, a controller for a brush-less motor that comprises stators and a rotor will be constructed to be of such a structure that signals indicating or representing angular position of the rotor are utilized to control electric currents applied to the stators, and characterized in that those signals output from the motor are preliminarily converted into a series of pulses.
In this controller, the pulse wave signals representing the rotor""s changing angular position are successively output to be processed subsequently, whereby various controls can be done in and by a superordinate control device receiving those signals and on the basis thereof, without aid of any rotary encoder, any tachometer or the like. Such a character of the present system is advantageous in that each motor controller can be driven accurately and without raising overall construction cost of the system. The xe2x80x9coverseeing device in charge of sophisticated controlsxe2x80x9d (viz., the superordinate control device) is thus separated from respective controllers for the brush-less motors. By virtue of this feature, those individual motor controllers are not only rendered inexpensive but also possible to quickly and immediately feed to the overseeing device the data on angular positions of the rotors, thus enabling the whole control system to be designed more freely and in a shorter time.
A conveyor system also provided herein comprises a central controller such as a sequencer or a controlling computer, and a plurality of roller conveyor units each composed in turn of a row of transverse rollers on and along which any desired articles are transported. Each conveyor unit comprises at least one brush-less motor for driving one of the transverse rollers and a controller for controlling the brush-less motor composed of stators and a rotor, wherein signals representing angular position of the rotor are utilized to control electric currents applied to the stators in such a manner that those signals output from the motor are preliminarily converted into pulse waves. This structure of the invention is applicable to a conveyor system in which the brush-less motor is built in the one transverse roller so as to form a xe2x80x9cmotor rollerxe2x80x9d.
In this conveyor system, an electronic circuit constituting each motor controller can be rendered simpler but capable of taking signals representing rotational speed of the brush-less motor, so that whatever manner or type of control can be done in compliance with the wishes of users. The central controller may receive and process the rotational speed signals to produce an overseeing command signal. Further, any intermediate controller such as a feedback control box or a master control box may intervene between the central controller and the individual terminal motor controllers. In this case, the intermediate controller will receive the overseeing signal from the central controller and the rotational speed signals from the terminal controllers so that a subordinate signal may be produced and fed thereto. Any other fashion of the system can also be employed herein to meet requirements from the users.